In recent years, on the strength of being thin and having a low power consumption, liquid crystal display devices are broadly used in laptop-type personal computers, mobile phones, information devices such as electronic organizers, camera-integrated VTRs having a liquid crystal monitor, and the like.
As a display mode which can realize a high contrast and a wide viewing angle, a vertical alignment mode utilizing a vertical-alignment type liquid crystal layer is drawing attention. In general, a vertical-alignment type liquid crystal layer is formed by using a liquid crystal material having negative dielectric anisotropy and vertical alignment films.
For example, Patent Document 1 discloses a liquid crystal display device whose viewing angle characteristics are improved by allowing an oblique electric field to be generated near an aperture that is provided in a counter electrode which opposes a pixel electrode via a liquid crystal layer, and around a liquid crystal molecule within the aperture which is in a vertical alignment state, allowing the surrounding liquid crystal molecules to take an inclined orientation.
However, with the construction described in Patent Document 1, it is difficult to form an oblique electric field across the entire region within the pixel. This leads to a problem in that regions in which the liquid crystal molecules have a slow response to voltage occur within the pixel, thus causing an afterimage phenomenon.
In order to solve this problem, Patent Document 2 discloses a technique in which, regularly-arranged apertures are provided in the pixel electrode or the counter electrode to form a plurality of liquid crystal domains exhibiting radially-inclined orientation within the pixel.
Moreover, Patent Document 3 discloses a technique which involves regularly providing a plurality of protrusions within the pixel to form liquid crystal domains in radially-inclined orientation that are centered around the protrusions.
Furthermore, Patent Document 4 discloses a technique in which the radially-inclined orientation of liquid crystal domains which are formed by orientation restriction structures provided on one of the substrates is stabilized by the orientation restriction force of protrusions which are provided on the other substrate.
On the other hand, in recent years, a liquid crystal display device which is capable of high-quality displaying in both outdoor and indoor situations has been proposed (e.g. Patent Documents 5 and 6), and is used in electronic equipment for mobile use, e.g., mobile phones, PDAs, and hand-held game machines. This liquid crystal display device, which is referred to as a transflective type (or transmission/reflection combination type) liquid crystal display device, has a reflection region which presents display in a reflection mode and a transmission region which presents display in a transmission mode, both within the pixel.
An ECB mode, a TN mode, and the like are used for transflective type liquid crystal display devices which are commercially available at present. Patent Document 3, supra, discloses a construction in which the vertical alignment mode is applied not only to a transmission type liquid crystal display device but also to a transflective type liquid crystal display device.
[Patent Document 1] Japanese Laid-Open Patent Publication No. 6-301036
[Patent Document 2] Japanese Laid-Open Patent Publication No. 2000-47217
[Patent Document 3] Japanese Laid-Open Patent Publication No. 2003-167253
[Patent Document 4] Japanese Laid-Open Patent Publication No. 2003-315803
[Patent Document 5] Japanese Patent No. 2955277
[Patent Document 6] specification of U.S. Pat. No. 6,195,140